KR20140126418A - Method for treating acidic gas - Google Patents

Abstract

SUMMARY OF THE INVENTION An object of the present invention is to improve the defective treatment of the acid gas due to the measurement delay of the acid gas measuring device and the excessive addition of the alkaline agent in the feedback control without introducing a new expensive acid gas measuring device.
The acidic gas treatment method includes a step of setting a range of inclination of at least two acid gas concentrations, a step of setting a control target value of the acidic gas concentration by at least two ranges of inclination, And a step of calculating a control output value indicating an addition amount of the alkali agent on the basis of the control target value. In the step of setting the control target value, the control target value to be set when the range of the gradient of the acid gas concentration is large (when the gradient of the increase in the acid gas is increased) is smaller than the range of the gradient of the acid gas concentration Is smaller than the control target value set for the time (t).

Description

[0001] METHOD FOR TREATING ACIDIC GAS [0002]

The present invention relates to a method for producing harmful hydrogen chloride (hydrogen sulfide) or sulfur oxide (sulfur oxide) generated in a combustion facility such as a municipal waste incinerator, an industrial waste incinerator, a power generation boiler, a carbonization furnace, The present invention relates to a method of treating an acidic gas. And more particularly, to a method for efficiently controlling the amount of an alkali agent for treating an acidic gas.

Exhaust gas containing harmful hydrogen chloride or sulfur oxides is treated by an alkali agent such as slaked lime or sodium hydrogen carbonate and then is collected by a dust collector such as a bag filter And then discharged from the chimney. On the other hand, fly ash collected in the dust collector contains harmful heavy metals such as Pb and Cd, and these harmful heavy metals are stabilized and then landfilled.

Sodium bicarbonate processed with a fine powder of 5 to 30 m, which is an alkaline agent for treating an acid gas, has high reactivity as compared with slaked lime, so that acidic gas can be stably treated and unreacted contents can be reduced, This is an effective means for reducing the environmental load. As a treatment method for heavy metals, a method of insolubilization treatment by chelate such as diethyldithiocarbamate is generally used. In the short term, heavy metal fixing effect (heavy metal fixing effect) is high, At the final disposal site, the problem of re-elution of heavy metals such as lead is caused by pH drop by acid rain and oxidative autolysis of the chelate (oxidation self-decomposition). On the other hand, heavy metal fixation by phosphoric acid or other phosphoric acid compounds changes to the form of hydroxyapatite which is an inorganic mineral. Therefore, it is excellent in long-term stability at the final disposal site, . Also, the method of treating fly ash treated with the above-mentioned fine powder sodium hydrogen carbonate with a heavy metal fixing agent such as phosphoric acid is an effective means having a large effect of reducing the environmental load.

However, controlling the addition amount of alkali metal such as calcium hydroxide or sodium hydrogencarbonate to treat the acidic gas such as hydrogen chloride or sulfur oxide not only can reduce the cost of the acid gas treatment but also reduces the unreacted components of the alkali agent, An effect of reducing the amount of landfill can be expected.

The amount of the alkali agent to be used for treating the acidic gas such as hydrogen chloride or sulfur oxide is generally determined based on the hydrogen chloride concentration measured by an ion electrode type (ion electrode type) hydrogen chloride measuring device provided at the rear stage of the bag filter, And feedback control is performed by the control device. However, in a combustion facility such as an incineration facility, a device for measuring the acidic gas concentration at the inlet is not installed, and the control output is adjusted by setting a parameter of the PID control in a state of unknown change of the inlet. However, since the PID controller has five setting items P, I, D, the lower limit of addition (output) and the upper limit of addition (output), and the set values of each item are combined to define the control output value, It takes a great deal of time. Therefore, in many cases, the setting by the PID controller generally controls the addition amount to be significantly increased when the control target value (SV) is exceeded.

However, the control output of the normal PID control device can be set only to a single upper limit, and for example, when the control target value SV of the HCl concentration is set to 40 ppm, a single upper limit of the control output at a concentration of 40 ppm or more It is necessary to add an alkali agent, which causes excessive addition of the alkali agent. In addition, the feedback control is affected by the measurement delay of the acid gas measuring device. The concentration of hydrogen chloride at the outlet of the bag filter is measured by a usual ion electrode method (for example, HL-36, a product of Kyotote Electronics Engineering Co., Ltd. in Japan), and the sulfur oxide concentration is measured by an infrared absorption method (NSA-3080, product of Shimadzu Corporation, Japan). However, if the sampling time of the sample exhaust gas and the response time of the measuring instrument are included, there is an enormous measurement delay of 5 to 10 minutes. This measurement delay causes an addition lag of an alkali agent, which leads to an unsatisfactory treatment of an acid gas and causes an excessive addition of an alkali agent.

Various control methods have been studied to solve this problem. In Patent Document 1, " P + PID control " for further adding P to a normal PID control system has been proposed. This proposal considers the correspondence of the unexpected occurrence of the acid gas which is difficult in the normal PID control. In Patent Documents 2 and 3, feedforward control (feedforward control) for determining the addition amount of the alkali agent based on the acid gas concentration at the inlet and addition of the alkali agent based on the acid gas concentration after the alkali agent treatment A control method of combining feedback control has been proposed. This control system is expected to have an effect of suppressing the excessive addition of the feedback control, and it is believed that the effect of reducing the acid gas stabilization treatment and the excessive addition of the alkali agent can be obtained.

: Japanese Patent Application Laid-Open No. 2002-113327 : Japanese Patent Application Laid-Open No. 10-165752 Japanese Unexamined Patent Application Publication No. 2006-75758

However, in Patent Document 1, unexpected response of the inlet is possible to some extent, but the measurement delay of the measuring device is not taken into consideration, so that it can not cope with the processing failure of the acid gas due to the addition lag of the alkali agent due to the measurement delay. In Patent Documents 2 and 3, most of the facilities which do not measure only the acid gas concentration at the outlet in the combustion facility such as the incinerator are used. In order to implement this control system, the higher value It is necessary to introduce a new acid gas measuring device of the present invention.

SUMMARY OF THE INVENTION The present invention has been made in view of the above conventional circumstances and it is an object of the present invention to suppress the generation of an acid gas and an excessive addition of an alkali agent due to a measurement delay of a conventional feedback control in a feedback format in which it is not necessary to introduce an expensive new acid gas measuring device And a method for treating an acidic gas.

(One). An acidic gas treatment method for feedback-controlling an addition amount of an alkali agent based on a measurement signal of an acidic gas measuring apparatus installed in a process after an alkali agent is added to an acidic gas contained in a combustion exhaust gas, characterized by comprising: (For example, a 6-second average of the most recent HCl concentration gradient to be described later, a positive range and a negative range); and a step of setting the acid gas concentration (For example, 30 ppm or 40 ppm in the first embodiment to be described later) of a control target value of the alkaline agent on the basis of at least the measurement signal and the control target value Wherein, in the step of setting the control target value, when the range of inclination of the acid gas concentration is large (For example, when the 6-second average of the most recent HCl concentration gradient is fixed (when the acid gas tends to increase)), when the range of the gradient of the acid gas concentration is small (When the 6-second average of the most recent HCl concentration gradient, which will be described later, is negative) (when the acid gas is in a decreasing tendency)).

In the conventional PID control, for example, when the control target value SV of the acid gas concentration is set to 40 ppm, the control output is increased after reaching 40 ppm to add the alkali agent, and the added alkali agent reacts with the acid gas The control output decreases after the acid gas concentration reaches 40 ppm or less. Therefore, the tendency of increasing or decreasing the concentration of the acid gas was not considered.

On the other hand, according to (1), since the target value of the control of the acid gas concentration in the increasing tendency of the acid gas is made smaller than the target value of the acid gas concentration in the decreasing tendency, the control output value of the adding amount of the alkali agent at the increasing tendency of the acid gas Becomes larger than the control output value at the time of the tendency.

(2). (1), the lower limit value of the control output value indicating the addition amount of the alkali agent (for example, LH (control output lower limit) shown in Figs. 15, 17 and 19 (The maximum addition amount of the fine powdery sodium hydrogencarbonate) (for example, LH (control output upper limit) in Fig. 15, Fig. 17 and Fig. 19 to be described later) and the upper limit value (For example, the control output addition amount shown in Figs. 15, 17 and 19, which will be described later) of the control output value corresponding to the BF outlet HCl concentration in Fig. 15, Fig. 17 and Fig. Wherein the acidic gas treatment step further comprises the step of treating the acidic gas.

Since the conventional PID control device has only one control output upper limit, for example, if the control target value SV of the acid gas is constant, the alkali agent is added to the upper limit value regardless of the acidic gas concentration, It causes. On the other hand, according to (2), it is possible to appropriately add the alkaline agent according to the magnitude of the acid gas concentration by limiting the control output according to the current acid gas concentration (step control method described later) .

(3). In the acidic gas treatment method described in (1) or (2), the acid gas measuring device is a hydrogen chloride concentration measuring device by ion electrode method.

(4). A method for treating an acidic gas according to any one of (1) to (3), wherein the acid gas measuring apparatus is an apparatus for measuring sulfur oxide concentration by an infrared absorption method or an ultraviolet fluorescence method.

The apparatus for measuring an acidic gas used in the present invention can be carried out without depending on a measurement system. The concentration of hydrogen chloride can be measured by ion electrode method, single absorption line absorption spectroscopy by laser, etc., and sulfur oxides can be measured by infrared absorption method, ultraviolet fluorescence method and the like. Further, since the present invention is primarily aimed at improving the measurement delay of the acid gas, it is possible to use a sulfur oxide measuring device by a hydrogen chloride measuring device, an infrared absorption method, or an ultraviolet fluorescence method, It is particularly effective in a facility where feedback control is performed by measuring the acid gas at the rear end.

In addition, in the combustion facility, there is a possibility that the excessive addition of the feedback control can be improved by measuring the concentration of hydrogen chloride at the downstream of the bag filter by a laser type without measurement delay and performing feedback control. However, the technical problem in the laser method remains as a technical problem in the JIS certification, and thus it has not been widely used as a measuring device for determining the concentration of the acid gas of the final exhaust gas.

(5). (1) to (4), the inclination of the concentration of the acid gas for setting the control target value is set to an average value within the most recent 7 minutes.

It is preferable to use the average value within the latest 7 minutes as the slope of the acid gas concentration for setting the control target value. When the average value of the inclination of the acid gas within 7 minutes is used, an appropriate selection becomes possible, and the acid gas can be stably treated.

(6). (1) to (5), the addition amount of the alkali agent is controlled by using both the output of the control output calculated from the hydrogen chloride concentration and the control output calculated from the sulfur oxide concentration .

In combustion facilities of industrial waste incinerators and civilian factories, hydrogen chloride and sulfur oxides often occur at high concentrations. In this case, both the hydrogen chloride and the sulfur oxide are to be treated, and the control output and the sulfur oxide concentration (sulfur oxide concentration) obtained based on the hydrogen chloride concentration (hydrogen chloride concentration) For example, by adding the control output obtained on the basis of the hydrogen concentration of the hydrogen chloride and the sulfur oxide, for example, to stably treat both acid gases of hydrogen chloride and sulfur oxide.

(7). The method for treating an acidic gas according to (1) or (6), wherein the alkali agent for treating the acidic gas is fine powder sodium hydrogencarbonate having an average particle diameter of 5 to 30 m.

The alkali agent used in the present invention is preferably fine powder sodium hydrogencarbonate whose reactivity with an acidic gas is fast and whose average particle diameter is adjusted to 5 to 30 mu m. Since the reactivity of the fine powder sodium hydrogencarbonate is fast, the control response is good, and the performance of the present invention can be effectively exerted. However, the present invention is based on a control method, and can be applied to slaked lime. The slaked lime can exhibit the performance of the present invention because the slaked lime has a high reactivity with the acid gas and has a specific surface area (specific surface area) of, for example, 30 m ² / g or more.

According to the present invention, in the feedback type that does not require the introduction of an expensive new acid gas measuring device, improvement in the treatment failure of the acid gas due to measurement delay of the acid gas measuring device of the conventional feedback control and excessive addition of the alkali agent It is possible to treat the acid gas stably by adding the alkali agent efficiently.

1 is a block diagram showing the construction of an acidic gas treatment system 1 in which fine powder sodium bicarbonate is added to HCl which is an exhaust gas in an incineration facility.
Fig. 2 is a basic configuration diagram of the simulation reaction system 1. Fig.
3 is a graph showing the relationship between the added amount of fine powdery sodium hydrogencarbonate and the HCl removal rate.
4 is a graph showing the behavior of HCl concentration at the outlet of the bag filter in an actual device.
5 is a graph showing the behavior of HCl concentration at the outlet of the bag filter in the simulation reaction system 1.
Fig. 6 is a basic configuration diagram of the simulation reaction system 2.
7 is a graph showing the relationship between the added amount of fine powdery sodium hydrogencarbonate and the HCl removal rate in the exhaust gas reaction.
8 is a graph showing the relationship between the added amount of fine powdery sodium hydrogencarbonate and the HCl removal rate in the reaction on the bag filter.
9 is a graph showing the behavior of HCl concentration at the outlet of the bag filter in the simulation reaction system 2.
10 is a table showing HCl concentration at the outlet of the bag filter for each of Comparative Examples and Examples.
11 is a graph showing the behavior of inlet HCl concentration.
12 is a graph showing the behavior of the addition amount of the fine powder sodium hydrogencarbonate and the outlet HCl concentration in Comparative Example 1. Fig.
13 is a graph showing the behavior of the addition amount of the fine powder sodium hydrogencarbonate and the outlet HCl concentration in Example 1. Fig.
14 is a graph showing the behavior of the addition amount of the fine powdered sodium hydrogencarbonate and the outlet HCl concentration in Example 2. Fig.
15 is a table showing control settings of the step control system in the second comparative example.
16 is a graph showing the behavior of the addition amount of the fine powdered sodium hydrogencarbonate and the outlet HCl concentration in Comparative Example 2. Fig.
17 is a table showing control settings of the step control system in the third embodiment.
18 is a graph showing the behavior of the addition amount of the fine powdered sodium hydrogencarbonate and the outlet HCl concentration in Example 3. Fig.
19 is a table of control settings of the step control system in the fourth embodiment and the like.
20 is a graph showing the behavior of the addition amount of the fine powdered sodium hydrogencarbonate and the outlet HCl concentration in Example 4. Fig.
21 is a graph showing the behavior of the addition amount of the fine powder sodium hydrogencarbonate and the outlet HCl concentration in Example 5. Fig.
22 is a graph showing the behavior of the addition amount of the fine powdered sodium hydrogencarbonate and the outlet HCl concentration in Example 6. Fig.
23 is a graph showing the behavior of the addition amount of the fine powder sodium hydrogencarbonate and the outlet HCl concentration in Example 7. Fig.
24 is a graph showing the behavior of the addition amount of the fine powder sodium hydrogencarbonate and the outlet HCl concentration in Example 8. Fig.

Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited thereto.

1 is a block diagram showing the construction of an acidic gas treatment system (1) in which fine powder of sodium hydrogen carbonate is added to HCl which is an exhaust gas in an incineration facility.

The acid gas treatment system 1 comprises a control device 11, a fine powder sodium bicarbonate addition device 12, a bag filter 13 and an HCl concentration measurement device 14 have. The control device 11 calculates the control output value of the added amount of fine powdery sodium hydrogencarbonate based on the HCl concentration measurement signal or the like by the PID control method. The fine powder sodium hydrogencarbonate addition device 12 adds fine powdery sodium hydrogencarbonate to HCl in the exhaust gas based on the control output value of the added amount of fine powdery sodium bicarbonate calculated by the control device 11. [

The bag filter 13 removes dust after the reaction of HCl in the exhaust gas and sodium bicarbonate powder. The HCl concentration measuring device 14 is a device for measuring the concentration of fine particles of sodium bicarbonate accumulated on the bag filter 13 by accumulating on the bag filter 13 the fine powder sodium bicarbonate remaining due to reaction with HCl in the exhaust gas ) And the HCl concentration (HCl concentration at the outlet of the bag filter to be described later) after the HCl reaction after the exhaust gas reaction is measured, and transmits the HCl concentration measurement signal to the control device 11.

The acidic gas treatment system 1 repeats this cycle to perform feedback control so that the control device 11 controls the control output value of the added amount of fine powdered sodium hydrogencarbonate to be appropriate.

The HCl concentration measuring device 14 is a hydrogen chloride concentration measuring device of the ion electrode type (ion electrode type).

1, the HCl concentration (the concentration of the back filter outlet HCl to be described later) after the reaction of the fine powder sodium hydrogencarbonate accumulated on the bag filter 13 and the HCl after the exhaust gas reaction was measured, 14 is preferably provided. This is because the fine powder sodium hydrogencarbonate remaining by the reaction with HCl in the exhaust gas is accumulated on the bag filter 13 and the accumulated fine powder sodium bicarbonate reacts with the HCl after the exhaust gas reaction, So that the concentration can be measured.

Further, the HCl concentration measuring device 14 is not limited to the above, and any process may be performed after adding fine powdered sodium hydrogencarbonate to the HCl in the exhaust gas by means of the fine powder sodium hydrogencarbonate addition device 12 good.

The control performed by the control device 11 will be described in detail.

The control device 11 sets two ranges in which the gradient of the HCl concentration (the rate of change of the concentration time rate) is a positive range and a negative range. The control target value of the HCl concentration is set for each of the two ranges.

Here, the setting of the control target value of the HCl concentration makes the control target value set for the range where the inclination of the HCl concentration is fixed smaller than the control target value for the non-denial range. By doing so, the control output value of the added amount of fine powdery sodium hydrogencarbonate at the time of increasing the HCl concentration can be made larger than the control output value at the time of decreasing the HCl concentration.

In addition, when the HCl concentration tends to decrease, the addition amount of the fine powdered sodium hydrogencarbonate may be directly decreased by performing control such that the output value of the added amount of fine powdered hydrogencarbonate is increased to, for example, 0.7 times. By doing so, the amount of addition can be quickly lowered when the HCl concentration tends to decrease, and the excess addition can be reduced.

Next, the step control method (step control method) will be described by changing the control method in the control device 11 from the PID control method.

The step method is a control method that sets the control output stepwise according to the HCl concentration. Specifically, in addition to the upper limit value of the control output value set in the PID control method, a new upper limit value of the control output value is set corresponding to the HCl concentration.

Here, in the ordinary PID control, since the upper limit value of the added amount of the fine powdery sodium bicarbonate is only one, the fine powder sodium hydrogen carbonate is added in the range of reaching the upper limit value regardless of the HCl concentration, . By adopting the step control method, the addition of the new control output upper limit value according to the present HCl concentration makes it possible to appropriately add the alkaline agent according to the magnitude of the acidic gas concentration, and it becomes possible to suppress excessive addition of the added amount.

Here, a new control output upper limit value is set corresponding to the HCl concentration, but the higher the HCl concentration, the higher the new control output upper limit value. However, in order to suppress the excessive addition of the alkali agent, the upper limit value of the control output value set in the PID control method (for example, LH (control output upper limit) shown in Figs. 15, 17 and 19 Value.

As an example of the setting of the new control output upper limit value, as the control output addition amount corresponding to the BF outlet HCl concentration (calculation input value) described in Figs. 15, 17 and 19 described later becomes higher, the new control output upper limit value becomes higher .

The acidic gas measuring device used in the present embodiment is not limited to the hydrogen chloride (HCl) concentration measuring device (the HCl concentration measuring device 14) and may be an infrared absorption method or an ultraviolet fluorescent method May be a sulfur oxide concentration measuring device.

In the present embodiment, the slope of the acid gas concentration for setting the control target value of the HCl concentration is an average value within the latest 7 minutes. When the average value of the inclination of the acid gas within 7 minutes is used, proper selection is possible and the acid gas can be stably treated.

Further, in the present embodiment, only the control output calculated from hydrogen chloride is used, but the addition amount of the alkali agent may be controlled using both the control output calculated from the hydrogen chloride concentration and the control output calculated from the sulfur oxide concentration. In combustion facilities of industrial waste incinerators and civilian factories, hydrogen chloride and sulfur oxides often occur at high concentrations.

In this case, both the hydrogen chloride and the sulfur oxide are to be treated, and the control output obtained based on the hydrogen chloride concentration (hydrogen chloride concentration) of the hydrogen chloride concentration measuring apparatus installed at the rear end of the bag filter and the sulfur oxide concentration Concentration), for example, can be stably treated with both acid gases of hydrogen chloride and sulfur oxide.

The fine powdered sodium hydrogencarbonate used in the present embodiment is preferably a fine powdered sodium hydrogencarbonate having a high reactivity with an acidic gas and an average particle diameter adjusted to 5 to 30 mu m. This is because the reactivity of the fine powder sodium hydrogencarbonate is fast and the control response is good.

In this embodiment, fine powder sodium hydrogencarbonate is used as the alkaline agent, but there is no particular limitation on the alkaline agent exhibiting the effect of the present embodiment. Examples of the alkaline agent other than the fine powder sodium hydrogencarbonate include sodium carbonate, potassium hydrogen carbonate, potassium carbonate, sodium sesquicarbonate, natural soda, sodium hydroxide, potassium hydroxide, magnesium oxide, magnesium hydroxide and the like. When the alkali agent is a powder, it is preferable that the fine powder having a particle diameter of less than 30 μm, especially 5 to 20 μm, which has high reactivity with an acid gas. A powder having a particle diameter adjusted in advance may be applied, or an alkaline agent having a large particle size may be added while pulverizing it locally by providing a crushing facility on the site (local site).

In addition, in the combustion facility measuring the acid gas at the inlet, it is also effective to feed back and control by this control method in addition to the feedforward control. In the case where a denitration catalyst device is provided at the downstream of the bag filter, it is necessary to apply the filter at around 200 ° C. Therefore, by adjusting the temperature of the bag filter to 180 to 230 ° C., (Thermal loss) can be reduced, and economical operation becomes possible.

Example

[Test Example 1]

A simulation reaction system was constructed from the results of the examination of actual equipment. First, the simulation reaction system 1 will be described as the first pattern. As a result of the examination of the actual equipment, it was confirmed that HIGHPURSER B-200, a product of KURITA INDUSTRIAL CO., LTD., Japan, which had been adjusted to an average particle size of 8 mu m, (Product HL-36, manufactured by Kyoto Electronics Co., Ltd., Japan) using a PID device, which is a control device of the fuel cell.

[Simulation Reaction System 1]: The reaction in the exhaust gas is assumed

In studying the simulation reaction system 1, the simulation reaction system 1 was configured as shown in FIG. 2, in which the reaction of sodium bicarbonate and hydrogen chloride (HCl) occurred in a very short time in the exhaust gas.

The basic configuration of the simulation reaction system 1 will be described with reference to Fig.

The chemical feed control in the incineration facility is based on the HCl concentration (after treatment) signal of the ion electrode type HCl concentration measuring apparatus installed at the outlet of the bag filter, (The amount of fine powder sodium hydrogen carbonate added (Ag)) is determined, and the determined addition amount of fine powdered sodium hydrogencarbonate (acidic gas treating agent) is added to the exhaust gas (inlet HCl concentration (Hi)). The fine powdered sodium hydrogencarbonate added to the flue gas reacts with an acidic gas such as HCl in the exhaust gas to remove HCl in the exhaust gas (removed based on the HCl removal rate [alpha]). Although the HCl concentration (Ho) of the outlet of the bag filter after the present reaction is measured by the ion-electrode-type HCl measuring device, the measurement delay by the facility, the measurement delay by the exhaust gas sampling, And a control delay peculiar to the feedback occurs. Here, the measurement delay time (T) of HCl in this simulation was set as shown in the following equation (1).

T = T1 + T2 + T3 ... ... (One)

T: Measurement delay time of simulation reaction system

T1: Facility delay time (sec) [30sec setting]

T2: Exhaust gas sampling time of the HCl measuring device (sec) [240 sec setting]

T3: 90% response time of HCl measurement device (sec) [180sec setting]

In addition, the diffusion of HCl gas into the absorption liquid affects the 90% response time (measurement delay) of the ion electrode type, so T3 is given by the following equation (2). In this simulation review, the measurement delay time of this simulation is set to T1 = 30 seconds, T2 = 240 seconds, and T3 = 180 seconds from the situation of the facility.

T3 = 2.3 x? ... (2)

Y _n = Y _{n -1} + (X _n - Y _{n -1} ) ÷ τ × Ts ... ... (3)

τ: Time constant (sec)

Ts: Unit simulation time (= data sampling time) (sec) [0.5sec setting]

X _n : current measuring instrument input HCl concentration (ppm)

Y _n : Current measuring device output HCl concentration (ppm)

Y _{n -1} : Measurement device output HCl concentration (ppm) of the previous [Ts (sec)

The HCl removal rate (?) Of the inlet HCl concentration (Hi) by the fine powder sodium hydrogencarbonate was calculated from the application amount of the fine powder sodium hydrogencarbonate (J) and the HCl removal rate (Fig. 3). The reaction between HCl and fine powder sodium hydrogen carbonate was carried out for a very short time. The addition amount (J) of the fine powder sodium hydrogen carbonate is calculated by the following equation (4).

J = Ag ÷ {Hi ÷ 0.614 ÷ 1000 ÷ M1 × M2 × F ÷ 1000} ... ... (4)

J: fine powder sodium hydrogen carbonate added equivalent

Ag: fine powder Sodium hydrogen carbonate addition amount (kg / h)

Hi: inlet HCl concentration (ppm)

M1: HCl molecular weight [set to 36.5]

M2: Sodium bicarbonate Molecular Weight [Set to 84]

F: amount of exhaust gas (Nm ³ / h) [set to 25,000Nm ³ / h]

P (proportional gain) = 10%, I = 0.1 seconds, D = 0.1 seconds, the amount of addition output lower limit of 5 kg / h, the same PID control conditions as those of the actual equipment to which fine powder sodium hydrogencarbonate was added, , And the addition amount output upper limit of 100 kg / h ", the behavior of the outlet HCl concentration (Ho) in the simulation and the actual instrument became different from each other (FIGS. 4 and 5). The outlet HCl concentration (Ho) is calculated by the following equation (5).

Ho = Hi x (1 -? G / 100) ... ... (5)

Hi: inlet HCl concentration (ppm)

Ho: Back filter outlet HCl concentration (ppm)

α: HCl removal rate (%) [Setting from the relationship between the addition equivalent and the HCl removal rate (FIG. 3)]:

Comparing the transition of the HCl concentration after the HCl treatment with the addition of the fine powder sodium hydrogencarbonate, the rising rate of the HCl concentration of the present simulation reaction system 1 is faster than that of the actual equipment. The parameters such as the measurement delay time and the like were examined and changed, and the results of the simulation with the actual apparatus did not coincide with each other. Therefore, it is considered that the above-mentioned increase rate of the HCl concentration in the actual equipment is delayed compared to the simulation reaction system 1 because the unreacted fine powder sodium hydrogencarbonate collected by the bag filter reacts with HCl.

[Test Example 2]

Next, the simulation reaction system 2 will be described as a second pattern.

[Simulation Reaction System 2]: Combined reaction on exhaust gas and bag filter

The reaction on the bag filter was constructed as shown in Fig. 6 by adding to the reaction in the exhaust gas in consideration of the reaction between unreacted fine powdery sodium hydrogencarbonate and HCl on the bag filter. The retention time of the collected product in the bag filter is usually about 2 hours. Therefore, in this simulation reaction system 2, the fine powder sodium bicarbonate on the bag filter was made to disappear at a prescribed time (set to about 2 hours).

The basic configuration of the simulation reaction system 2 will be described with reference to Fig.

First, in the chemical injection control in the incineration facility, based on the HCl concentration (after treatment) signal of the ion-electrode-type HCl concentration measuring apparatus installed at the outlet of the bag filter, the amount of chemical added (Ag)) is determined, and a determined amount of fine powdery sodium hydrogencarbonate (acid gas treating agent) is added to the exhaust gas (inlet HCl concentration (Hi)).

The HCl concentration (Hg) after the reaction in the exhaust gas is derived from the addition amount (Jg) of the fine powdery sodium hydrogencarbonate in the exhaust gas reaction and the exhaust gas reaction HCl removal rate (? G) (the following equation (6)). Further, the addition amount (Jg) of the fine powder sodium hydrogen carbonate in the exhaust gas reaction is calculated by the following equation (7).

Hg = Hi x (1 -? G / 100) ... ... (6)

Hi: inlet HCl concentration (ppm)

Hg: HCl concentration after exhaust gas reaction (ppm)

? g: HCl removal rate in the exhaust gas reaction (%)

[Setting from the relationship between the added amount of exhaust gas reaction fine powder sodium hydrogencarbonate and the HCl removal rate (FIG. 7)

Jg = Ag ÷ {Hi ÷ 0.614 ÷ 1000 ÷ M1 × M2 × F ÷ 1000} ... ... (7)

Jg: Exhaust gas reaction Micropowder Sodium bicarbonate Additive equivalent

Ag: fine powder Sodium hydrogen carbonate addition amount (kg / h)

Hi: inlet HCl concentration (ppm)

M1: HCl molecular weight [set to 36.5]

M2: Sodium bicarbonate Molecular Weight [Set to 84]

F: amount of exhaust gas (Nm ³ / h) [set to 25,000Nm ³ / h]

Further, the fine powder sodium hydrogencarbonate remaining by the exhaust gas reaction accumulates on the bag filter from time to time. The fine powder sodium bicarbonate accumulated on the bag filter reacts with HCl after the exhaust gas reaction to determine the HCl concentration (Ho) at the outlet of the bag filter. At this time, the fine powder sodium hydrogen carbonate amount (As) accumulated on the bag filter was obtained by subtracting the amount of fine powder sodium hydrogen carbonate reacted with HCl on the bag filter from the fine powder sodium hydrogen carbonate accumulated in the exhaust gas reaction.

Further, from the fine powdery sodium bicarbonate added equivalent (Js) on the bag filter, which is calculated experimentally from the amount of fine powder sodium hydrogen carbonate (As) accumulated on the bag filter and the concentration of HCl after the exhaust gas reaction (Hg) , The HCl concentration (Ho) at the outlet of the bag filter was determined (the following equation (8)). The addition amount (Js) of fine powdery sodium hydrogencarbonate on the bag filter is calculated by the following equation (9). Also, the delay of the HCl measurement was set to T (= T1 + T2 + T3) in the same manner as the simulation reaction system 1.

Ho = Hg x (1 -? S / 100) ... ... (8)

Hg: HCl concentration after exhaust gas reaction (ppm)

Ho: Back filter outlet HCl concentration (ppm)

? s: HCl removal rate of the reaction on the bag filter (%)

[Setting from the relationship between the added amount of fine powdery sodium hydrogencarbonate on the bag filter and the HCl removal rate (Fig. 8)

Js = As? {Hg / 0.614 / 1000 / M1? M2? F / 1000} ... (9)

Js: Sodium bicarbonate added to the fine powder on the bag filter Equivalent

As: Amount of fine powder sodium hydrogencarbonate on the bag filter (kg / h)

Hg: HCl concentration after exhaust gas reaction (ppm)

M1: HCl molecular weight [set to 36.5]

M2: Sodium bicarbonate Molecular Weight [Set to 84]

F: amount of exhaust gas (Nm ³ / h) [set to 25,000Nm ³ / h]

As = Zn / Ts x 3600 ... ... (10)

Z _n : Accumulated amount of fine powder hydrogencarbonate on bag filter (kg)

Ts: unit simulation time (= data sampling time) (sec)

[0.5sec setting]

Z _n = Z _{n '} × (1 - 2.3 / T 4 × Ts) ... (11)

Z _{n '} : Unreacted fine powder Sodium bicarbonate (kg)

T4: Fine powder accumulated on the bag filter Sodium hydrogencarbonate 90% Decay time (sec)

[7,200 sec setting]

Ts: unit simulation time (= data sampling time) (sec)

[0.5sec setting]

Z _{n '} = (Ag ÷ 3600 × Ts - Rg) + (Z _{n -1} - Rs) ... (12)

Ag: fine powder Sodium hydrogen carbonate addition amount (kg / h)

Ts: unit simulation time (= data sampling time) (sec)

[0.5sec setting]

Rg: reaction amount of sodium hydrogencarbonate in exhaust gas reaction (kg / h)

Z _{n -1} : Accumulated amount of sodium bicarbonate (kg) on the bag filter before Ts (sec)

Rs: Reaction amount of sodium hydrogencarbonate in the reaction on the bag filter (kg / h)

Rg = (Hi ÷ 0.614 ÷ 1000 ÷ M1 × M2 × F ÷ 1000) ÷ 3600 × Ts × αg ÷ 100 ... (13)

Hi: inlet HCl concentration (ppm)

M1: HCl molecular weight [set to 36.5]

M2: Sodium bicarbonate Molecular Weight [Set to 84]

F: amount of exhaust gas (Nm ³ / h) [set to 25,000Nm ³ / h]

? g: HCl removal rate in the exhaust gas reaction (%)

Rs = (Hg ÷ 0.614 ÷ 1000 ÷ M1 × M2 × F ÷ 1000) ÷ 3600 × Ts × αs ÷ 100 ... (14)

Hg: HCl concentration after exhaust gas reaction (ppm)

M1: HCl molecular weight [set to 36.5]

M2: Sodium bicarbonate Molecular Weight [Set to 84]

F: amount of exhaust gas (Nm ³ / h) [set to 25,000Nm ³ / h]

? s: HCl removal rate of the reaction on the bag filter (%)

In the present theory, simulation was performed by changing the HCl removal rate due to the reaction in the exhaust gas and the reaction on the bag filter. As a result, the exhaust gas reaction and the reaction on the bag filter are shown in FIGS. 7 and 8 The HCl removal rate (95% of the exhaust gas reaction, 75% of the reaction on the bag filter) almost coincided with the behavior of the HCl concentration of the bag filter outlet (FIG. This is a result supporting that the HCl rising rate is relaxed because the fine powder sodium bicarbonate on the bag filter reacts with HCl. Also, in this simulation, the reaction with HCl on the bag filter is a result of being inferior to the exhaust gas reaction. It is considered that the reaction on the bag filter is due to the low HCl removal rate because the HCl concentration to be treated is low as compared with the exhaust gas reaction. It is considered that the fine powder sodium bicarbonate accumulated in the bag filter is pyrolyzed by the temperature of the exhaust gas to be sodium carbonate. Since the HCl removal rate of sodium carbonate is inferior to that of the fine powder sodium hydrogencarbonate, there is a possibility that the removal rate on the bag filter is lowered.

From the results of this examination, it is considered that the reaction between the fine powdery sodium hydrogencarbonate and HCl in the combustion exhaust gas is a reaction system in which the reaction in the exhaust gas and the reaction of the fine powder sodium bicarbonate accumulated on the bag filter are combined . In addition, since the behavior of the HCl concentration at the outlet of the bag filter is almost identical to that of an actual apparatus, it has been found that the present simulation reaction system 2 is effective as a tool for evaluating a control method using fine powder sodium hydrogencarbonate.

The results of examining various control methods in this simulation reaction system 2 are shown below. The mean particle size of the fine powdered sodium hydrogencarbonate used in Examples 1 to 8 below was 5 to 30 占 퐉. The HCl concentration measuring device 14 used in Examples 1 to 8 is a hydrogen chloride concentration measuring device by the ion electrode method.

[Comparative Example 1]

The PID control method "P (proportional gain) = 10%, I = 0.1 second, D = 0.1 second, the addition amount output lower limit 5 kg / h, the addition amount output upper limit 100 kg in the simulation reaction system 2 / h " by setting the control target value SV of the HCl treatment to 40 ppm. FIG. 10 shows the HCl concentration (average, maximum of 1 hour maximum, instantaneous maximum) of the bag filter outlet after the treatment with the fine powder sodium hydrogencarbonate and the fine powder sodium hydrogencarbonate. 12 shows the behavior of the fine powdery sodium hydrogencarbonate addition amount and the bag filter outlet HCl concentration during the present control.

[Example 1]

The control target value SV is set to 30 ppm in the case where the 6-second average of the latest HCl concentration gradient is positive in the same PID setting condition as the condition shown in Comparative Example 1, and the most recent HCl concentration gradient And the control target value (SV) was controlled to 40 ppm when the 6-second average was negative. Likewise, FIG. 10 shows the concentration (average, maximum of 1 hour maximum, instantaneous maximum) of the bag filter outlet HCl after the treatment with the fine powder sodium hydrogencarbonate and the fine powder sodium hydrogencarbonate. Fig. 13 shows the behavior of the fine powdery sodium hydrogencarbonate addition and the bag filter outlet HCl concentration in the present control.

It has been found that the control target value is set to a low value when the inclination of the HCl concentration is positive (increasing tendency), thereby increasing the amount of the fine powdery sodium bicarbonate added in the tendency of increasing the HCl concentration, thereby preventing the occurrence of the peak of HCl. In addition, the average of HCl and the maximum of 1 hour were also lowered, and the effect of stably treating HCl was obtained. However, this control is an appropriate control setting in a facility where it is necessary to stably treat the HCl concentration to, for example, 30 ppm or less, because the amount of the fine powdery sodium bicarbonate to be added increases compared to the conventional control (Comparative Example 1).

[Example 2]

The control target value SV is set to 30 ppm and the 6-second average of the latest HCl concentration slope is set to 30 ppm when the 6-second average of the most recent HCl concentration gradient is constant under the same PID setting condition as the condition shown in Comparative Example 1. [ The control target value (SV) was controlled to 50 ppm. Likewise, FIG. 10 shows the concentration (average, maximum of 1 hour maximum, instantaneous maximum) of the bag filter outlet HCl after the treatment with the fine powder sodium hydrogencarbonate and the fine powder sodium hydrogencarbonate. 14 shows the behavior of the fine powdery sodium hydrogencarbonate addition and the bag filter outlet HCl concentration in the present control.

In the case where the inclination of the HCl concentration was positive (increasing tendency), the effect of preventing the occurrence of HCl peaks was obtained in the same manner as in Example 1, and HCl was also stably treated as compared with the conventional control (Comparative Example 1). In addition, when the inclination of the HCl concentration is negative (decreasing tendency), the control target value SV is increased compared to Example 1, so that the addition amount of the fine powdery sodium bicarbonate decreases and the addition ends quickly, The addition amount of sodium was lower than that of Example 1. However, since the addition amount is increased as compared with the conventional control (Comparative Example 1), this control is an appropriate control setting in a facility where it is necessary to stably treat the HCl concentration to 30 ppm or less, for example.

Hereinafter, Comparative Example 2 and Examples 3 to 8 will be described. In Comparative Examples 2 and 3 to 8, the PID control method is replaced by a step control method.

The outline of the step control method will be described here. Unlike the PID control method, the step control method is a control method that specifies the output stepwise according to the HCl concentration at the outlet. 15), the control output is output stepwise between LO and LM1 when the HCl concentration is SV (control target value [control output start concentration (output lower limit or higher)]) to SM1 do. The control output is set to LM2 when the HCl concentration is between SM1 and SM2, and the LH (control output upper limit) is output when the HCl concentration is above SM2. In the normal PID control method, there is no output restriction, and only LO and LH are set. SVA1 and SVB1 are used to correct the table for determining the HCl concentration and the control output used in the HCl gradient control operation. When the HCl gradient is normal, SVA1 is subtracted from the HCl concentration used in the calculation. When the HCl gradient is negative, SVB1 was added to the HCl concentration used. Accordingly, the control output calculated when the same HCl concentration is input is larger than the control output value when the control output value when the value of the HCl gradient is large (the tendency of the acid gas concentration to increase) is smaller than the control output value when the value of the HCl gradient is small Respectively.

[Comparative Example 2]

The inlet HCl concentration shown in Fig. 11 is used to set the control target value (in this method, the concentration at which the control output of the alkaline agent is added at the output lower limit or higher is defined as SV) in the step control system in the simulation reaction system 2 is set to 40 ppm Respectively. FIG. 10 shows the HCl concentration (average, maximum of 1 hour maximum, instantaneous maximum) of the bag filter outlet after the treatment with the fine powder sodium hydrogencarbonate and the fine powder sodium hydrogencarbonate. The control output addition amount of the fine powdered hydrogencarbonate according to the HCl concentration at the outlet of the bag filter is shown in Fig. 16 shows the behavior of the addition amount of fine powdery sodium hydrogencarbonate and the HCl concentration at the outlet of the bag filter in the present control.

In this control method, since the control output is limited by the HCl concentration range between the lower limit and the upper limit of the control output, the alkali agent can be added stepwise. From this, excessive addition of the alkali agent was prevented, and the addition amount of the fine powder sodium hydrogencarbonate was considerably lowered. However, the treatment level of HCl to be treated was considerably deteriorated as compared with the conventional control (Comparative Example 1).

[Example 3]

In the same step control method as in Comparative Example 2, when the 6-second average of the most recent HCl concentration gradient is positive, the control target value SV is set to 30 ppm, and when the 6-second average of the most recent HCl concentration gradient is negative The control target value (SV) was controlled at 40 ppm. Likewise, FIG. 10 shows the concentration (average, maximum of 1 hour maximum, instantaneous maximum) of the bag filter outlet HCl after the treatment with the fine powder sodium hydrogencarbonate and the fine powder sodium hydrogencarbonate. The control output addition amount of the fine powdered sodium hydrogencarbonate according to the HCl concentration at the outlet of the bag filter is shown in Fig. 18 shows the behavior of the addition amount of the fine powdery sodium hydrogencarbonate and the HCl concentration at the outlet of the bag filter in the present control.

In this control method, an alkaline agent was added in a stepwise manner as in Comparative Example 2, and the effect of reducing the amount of sodium nano-sized hydrogencarbonate added was obtained as compared with the conventional control (Comparative Example 1). In addition, when HCl tends to increase, the effect of treating HCl stably by adding the fine powdery sodium hydrogencarbonate immediately in consideration of the measurement delay was obtained. This control method is a very effective method because the treatment level of HCl is improved as compared with the conventional control (Comparative Example 1), and the effect of reducing the amount of addition is obtained.

In this case, when the measurement value of the HCl concentration at the outlet of the bag filter is between 40 ppm and 50 ppm, the addition amount according to the HCl concentration is set and controlled. However, even if the range is controlled by the PID, The control output is limited to 50 kg / h or less when the HCl concentration is 50 ppm or less, and the control output is limited to 70 kg / h or less when the HCl concentration is 50 ppm to 60 ppm, so that it is considered that the equivalent HCl treatment effect and the effect of reducing the addition amount can be obtained.

[Example 4]

In the same step control method as in Comparative Example 2, when the 6-second average of the most recent HCl concentration gradient is positive, the control target value SV is set to 30 ppm, and when the 6-second average of the most recent HCl concentration gradient is negative The control target value (SV) was controlled to 50 ppm. Likewise, FIG. 10 shows the concentration (average, maximum of 1 hour maximum, instantaneous maximum) of the bag filter outlet HCl after the treatment with the fine powder sodium hydrogencarbonate and the fine powder sodium hydrogencarbonate. The control output addition amount of the fine powdered sodium bicarbonate according to the HCl concentration at the outlet of the bag filter is shown in Fig. 20 shows the behavior of the addition amount of the fine powdery sodium hydrogencarbonate and the HCl concentration at the outlet of the bag filter in the present control.

In this control method, since the control target value (SV) was increased in comparison with Example 3 when the fine powder sodium hydrogen carbonate was added stepwise and the HCl tended to decrease in the same manner as in Comparative Example 2, the addition amount of the fine powder sodium hydrogen carbonate And the addition was completed sooner, and the effect of reducing the addition amount as compared with the conventional control (Comparative Example 1) was obtained. In addition, although the amount of addition could be reduced, the treatment level of HCl was also equivalent to that of the conventional control (Comparative Example 1). This control method is also considered to be a very useful control method because it is possible to perform almost the same HCl treatment as in the conventional control and also to obtain an effect of reducing the amount of addition.

[Examples 5 to 8]

In order to examine the appropriate average time of the latest HCl concentration gradient that selects the control equation under the same control conditions as in Example 4, the slope-average time of the present HCl concentration was changed and examined. Likewise, FIG. 10 shows the concentration (average, maximum of 1 hour maximum, instantaneous maximum) of the bag filter outlet HCl after the treatment with the fine powder sodium hydrogencarbonate and the fine powder sodium hydrogencarbonate. 21 to 24 show the behaviors of the addition amount of fine powdery sodium hydrogencarbonate and the HCl concentration at the outlet of the bag filter in the present control.

As a result of this examination, when the average time of the slope of the HCl concentration for selecting the control formula was set to 10 minutes, a large HCl peak occurred (Example 8). This indicates that the timing of addition of the fine powdery sodium bicarbonate is delayed by lengthening the average time of the slope, and when it is set to more than 7 minutes, it indicates that the control is defective. On the other hand, when the average time was 7 minutes or less, the generation of abnormal HCl was not considered, and the average time of the proper HCl slope was considered to be 7 minutes or less (Examples 5 to 7).

Claims (7)

The amount of the acidic gas to be fed back is controlled based on the measurement signal of the acid gas measuring device (acid gas measuring device) installed in the process after adding the alkali agent to the acid gas contained in the combustion exhaust gas In the processing method of the present invention,
Setting a range of inclination of at least two acid gas concentrations;
Setting a control target value of the acidic gas concentration for each of the at least two ranges of inclination;
A step of calculating a control output value indicating an addition amount of the alkali agent based on at least the measurement signal and the control target value
Respectively,
In the step of setting the control target value, the control target value set when the gradient of the acid gas concentration is large is smaller than the control target value set when the range of the gradient of the acid gas concentration is small Characterized in that the acidic gas is treated by a method comprising the steps of:
The method according to claim 1,
Further comprising the step of setting at least one new upper limit value of the control output value in correspondence with the concentration of the acid gas between a lower limit value and an upper limit value of the control output value indicating the addition amount of the alkali agent.
3. The method according to claim 1 or 2,
Characterized in that the acid gas measuring apparatus is a hydrogen chloride concentration measuring apparatus (hydrogen chloride concentration measuring apparatus) by ion electrode method.
The method according to any one of claims 1 to 3,
Wherein the acid gas measuring device is a sulfur oxide concentration measuring device (sulfur oxide concentration measuring device) by an infrared absorption method (infrared absorptive method) or an ultraviolet fluorescence method (ultraviolet light method).
The method according to any one of claims 1 to 4,
Wherein the inclination of the concentration of the acid gas for setting the control target value is set to an average value within the latest 7 minutes.
6. The method according to any one of claims 1 to 5,
Wherein the amount of the alkaline agent to be added is controlled by using both outputs of the control output calculated from the hydrogen chloride concentration and the control output calculated from the sulfur oxide concentration.
7. The method according to any one of claims 1 to 6,
Wherein the alkaline agent for treating the acidic gas is fine powder sodium hydrogen carbonate having an average particle diameter of 5 to 30 占 퐉.

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